Current experimental evidence points to the importance of nitric oxide in the preservation of normal vascular function and structure, blood pressure, sleep, appetite, and sexual function. It is also clear that nitric oxide activity is impaired in a wide array of cardiovascular disorders and that this deficit responds to administration of L-arginine, the sole substrate for generation of nitric oxide. Published studies in animals and our own preliminary findings in humans show that L-arginine levels decline with aging and could thus constitute a reversible contributor to development and progression of vascular dysfunction and other features of aging. We have also found that in the elderly, nutritional L-arginine supplementation can raise serum L-arginine levels to values comparable to those in younger subjects, but the functional implications of this effect remain unknown. This one year pilot proposal seeks to determine whether raising serum L-arginine levels with nutritional supplementation leads to increases in markers of nitric oxide activity, enhances endothelial, nitric oxide-mediated vasodilator function, and possibly improves subjective self-assessments of quality of sleep, daytime alertness, and appetite. This work could provide a theoretical foundation for studies of longer term supplementation with safe, inexpensive agents which could preserve cardiovascular and other functions in the elderly.